Regular articleCharacterization of microbial communities during start-up of integrated fixed-film activated sludge (IFAS) systems for the treatment of oil sands process-affected water (OSPW)

•IFAS-biofilms showed higher bacterial richness and diversity than IFAS-flocs.•Proteobacteria, Nitrospirae, Acidobacteria, and Bacteroidetes were the dominant phyla in IFAS flocs and biofilms.•Seed sludge microbial communities were significantly dissimilar in biomass collected from different IFAS systems.

In this study, integrated fixed-film activated sludge (IFAS) microbial development and degradation efficiency were investigated for oil sands process-affected water (OSPW) remediation. IFAS microbial community was characterized using 454 high-throughput 16S rRNA gene pyrosequencing that revealed that the IFAS seed sludge (activated sludge [AS] from the Gold Bar Wastewater Treatment Plant [GBWTP]) showed the greatest richness and evenness of bacterial community, as compare to other biomass samples. The Chao 1 value and the Shannon diversity index showed that the bacterial richness and microbial diversity in biofilms were significantly higher than those in flocs in both IFAS systems. Proteobacteria, Nitrospirae, Acidobacteria, and Bacteroidetes were dominant phyla in both flocs and biofilms in IFAS reactors. It is also noted that the phyla and class distributions of flocs and biofilms were significantly different. Principal coordinate analysis (PCoA) indicated that there were substantial differences between OSPW indigenous microbes and flocs and biofilm microbes in IFAS. Overall, a relatively low ozone dose (30 mg/L utilized) combined with IFAS reactor treatment significantly increased the organic contaminants removal. The combined ozonation and IFAS system showed the promise for OSPW treatment.